The invention relates generally to centrifugal couplings and, more particularly, to such couplings arranged as starting couplings to precede an automatic motor vehicle transmission, or installed as bridging couplings in a hydrodynamic torque converter.
It is possible in such couplings for vehicles, during a kick-dwn operation and the associated speed jumps, for example, for jolts to occur which may interfere considerably with riding comfort and possibly even damage components. These jolts or torque surges are attributable to the fact that, at high rotary speeds, the torque transmission capacity of the centrifugal coupling is a multiple of the engine torque and it is therefore impossible for a moderating speed slip to occur. If such a coupling were dimensioned so that it can just transmit the engine torque at high speeds, then at low speeds and high torques it would always operate in the slip range, which would result in considerable wear.
It is already known, from German Offenlegungsschrift (published unexamined patent application) No. 2,913,694, to divide the fly weight element of centrifugal couplings into two partial weights mutually connected by a spring, and to associate a primary side stop with the inner partial weight. Then, with increasing rotary speed, the inner partial weight contacts the stop so that with further increasing rotary speed only the outer partial weigh is effective as a source additional contact pressure. This results in a flattening of the centrifugal coupling torque curve (as shown in FIG. 7a) from the speed at which the inner partial weight contacts the stop (point A in FIG. 7a). However, torque surges during starting and shifting operations are nevertheless left out of consideration and not compensated for.
An object of the present invention is to provide a centrifugal coupling in which the torque curve can be influenced by starting and shifting operations as well as changes in the rotary speed, and which is particularly capable of reducing torque surges.
This and other objects of the present invention are attained in the provision of a centrifugal coupling with fly elements pressable against the internal surface of a friction drum counter to spring biasing forces wherein the fly elements each include at least two concentric partial weights mutually connected by radially-acting compression springs. The radial stroke of the inner partial weight or weights is limited by a primary side stop, so that from a specific primary speed any further increase in the centrifugal force from the inner partial weight directly acting upon the outer partial weight is prevented. The partial weights are further provided with check ramps, inclined in the circumferential direction, for a driver pin mounted on the primary side in order to give the torque curve of the coupling an optimum configuration. In some embodiments the check ramp on the outer partial weight may be replaced by a lever mounted on the primary side which transforms the force generated by the inner partial weight into a centripetal force acting upon the outer partial weight.
Other objects, features, and advantages of the present invention will become more apparent from the following description when taken with the accompanying drawings(s) which show, for purposes of illustration only, an embodiment/several embodiments in accordance with the present invention.